Meteorology · Clouds — Halo
A halo around the sun or moon, produced by ice crystals in cirrostratus, is often an early indication of:
- AA passing cold front already gone by
- BImminent clearing and high pressure
- CFog forming overnight
- DAn approaching warm front or deteriorating weather within a day or so✓ Correct
Explanation
High cirrostratus refracting light into a halo is part of the thickening cloud shield ahead of a warm front. Combined with a falling barometer and backing wind, it supports the old adage that a ring around the sun or moon foretells approaching wet weather.
Authority: Bowditch (Pub. No. 9), clouds and weather signs; WMO
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